Among thermoplastic resins, a polyester-series resin, has excellent mechanical and electrical properties, weather resistance, water resistance, and resistance to chemicals and solvents. Therefore, the resin is used as an engineering plastic in various purposes such as electric or electronic device parts, mechanical device parts and automotive parts. While, the polyester-series resin is required to have improved mechanical properties and to be flame-retardant from the viewpoint of safety as the field of their uses expands. In general, there is known a method for rendering the polyester-series resin flame-retardant by adding a flame retardant composed of a halogen-containing compound or an antimony-containing compound to the resin. However, the halogen-containing flame retardant is not preferable for environmental reasons because the flame retardant sometimes generates a large amount of a dioxin-series compound on resolution caused by combustion. Therefore, there is proposed a method for rendering the polyester-series resin flame-retardant by using a polycarbonate-series resin and a phosphorus-containing compound as a halogen-free flame retardant.
Japanese Patent Application Laid-Open No. 168297/1998 (JP-10-168297A) discloses a flame-retardant resin composition comprising a thermoplastic polyester resin, a polycarbonate-series resin, an organic phosphorus-series flame retardant, and a stabilized red phosphorus. Moreover, Japanese Patent Application Laid-Open No. 168295/1998 (JP-10-168295A) discloses a flame-retardant resin composition comprising a master batch composed of a polyester resin, a polycarbonate resin, a stabilized red phosphorus, and an olefinic resin.
The halogen-free flame retardant does not comprise harmful halogens, however, it is inferior to a halogen-series flame retardant in flame retardancy, so that it is necessary to add a large amount of the flame-retardant. The addition of a large amount of the flame-retardant brings about bleeding out (blooming) and deterioration in mechanical properties of a resin. Therefore, it is difficult to improve flame retardancy, mechanical properties and formability (or moldability).
On the other hand, there is also known a method for rendering the polyester-series resin flame-retardant by using a polyphenylene oxide resin and a phosphorus-containing compound. For example, Japanese Patent Application Laid-Open No. 47056/1985 (JP-60-47056A) discloses a thermoplastic resin composition in which a thermoplastic linear polyester resin, and a flame-retardant comprising a polyphenylene oxide resin, an organic phosphoric ester and a bromine-containing compound are blended. However, this method is not preferable for environmental reasons because of using a halogen-containing compound.
Therefore, it is contemplated that flame retardancy is imparted to a polyester resin without using a halogen-containing compound. For example, Japanese Patent Application Laid-Open No. 504563/1994 (JP-6-504563A) describes a resin composition comprising a polybutylene terephthalate, a polyphenylene oxide, and a resorcinol diphosphate. However, the resin composition has only approximately V-2 rank based on Flammability test UL-94, and does not have enough flame retardancy. Moreover, burning of the resin composition brings about dripping.
It is therefore an object of the present invention to provide a flame-retardant resin composition in which dripping has been inhibited, and a shaped article formed with the same.
It is another object of the present invention to provide a flame-retardant resin composition to which flame retardancy is imparted at a high level by using a halogen-free flame retardant without deteriorating properties of a base resin, and a shaped article formed with the same.